Spin-polarized Josephson current in superconductor/ferromagnet/superconductor junctions with inhomogeneous magnetization

Abstract

We study numerically the properties of spin-and charge-transport in a current-biased nanoscale diffusive superconductor|ferromagnet|superconductor junction when the magnetization texture is non-uniform. Specifically, we incorporate the presence of a Bloch/Neel domain walls and conical ferromagnetism, including the role of spin-active interfaces. The superconducting leads are assumed to be of the conventional s-wave type. In particular, we investigate how the 0-π transition is influenced by the inhomogeneous magnetization texture and focus on the particular case where the charge-current vanishes while the spin-current is non-zero. In the case of a Bloch/Neel domain-wall, the spin-current can be seen only for one component of the spin polarization, whereas in the case of conical ferromagnetism the spin-current has the three components. This is in contrast to a scenario with a homogeneous exchange field, where the spin-current vanishes completely. We explain all of these results in terms of the interplay between the triplet anomalous Green's function induced in the ferromagnetic region and the local direction of the magnetization vector in the ferromagnet. Interestingly, we find that the spin-current exhibits discontinuous jumps at the 0-π transition points of the critical charge-current. This is seen both in the presence of a domain wall and for conical ferromagnetism. We explain this result in terms of the different symmetry obeyed by the current-phase relation when comparing the charge-and spin-current. Specifically, we find that whereas the charge-current obeys the well-known relation Ic(φ) = −Ic(2π − φ), the spin-current satisfies Is(φ) = Is(2π − φ), where φ is the superconducting phase difference.

Nonequilibrium effects in a Josephson junction coupled to a precessing spin

“…Ho has a conical ferromagnetic structure whose magnetization rotates like a helix along the c axis. The appearance of spin-triplet correlations in such junctions and their effect on the long-range proximity effect 41,42 and spin currents 43 have also been studied theoretically. In the present problem, the magnetization direction varies in time rather than in space giving rise to time-dependent Andreev level dynamics and a dynamical inverse proximity effect in the form of induced time-dependent spintriplet correlations.…”

Preparation of a ferromagnetic barrier in YBa2Cu3O7–δ thinner than the coherence length

“…Recent observation of a supercurrent across the half-metal chromium dioxide [25][26][27] triggered intense activity to study triplet supercurrents (i.e., long range proximity effects) both theoretically [13][14][15] and experimentally. [16][17][18]28 Therefore the successful fabrication of oxide SFS-structures may help to investigate and understand the long-range proximity effects between d-wave high-T c superconductors and half-metal ferromagnetic LCMO layers.…”

Theoretical Study of Magnetism Induced by Proximity Effect in a Ferromagnetic Josephson Junction with a Normal Metal

“…[59][60][61] As well as the detection of STC by measuring the Josephson critical current and T C as mentioned above, the spin-dependent transport of STC in S/F hybrid junctions gives a direct evidence of spin in the STC . 22,29,[62][63][64][65][66][67][68] One of the simplest quantity induced by the spin of the STC is a magnetization induced by the proximity effect of STC . 22,29,62,65,67) In F/S junctions, the STC is also induced to S by the inverse proximity effect.…”

“…22,29,[62][63][64][65][66][67][68] One of the simplest quantity induced by the spin of the STC is a magnetization induced by the proximity effect of STC . 22,29,62,65,67) In F/S junctions, the STC is also induced to S by the inverse proximity effect. [69][70][71][72][73] The magnetization induced by spin of STC is a good fingerprint to establish the existence of STC.…”

“…Moreover, when the magnetization in the F is non-uniform in a S/F junction, the STC formed by electrons of equal spin (|S z | = 1) can also be induced in the F. This includes cases, for instance, where the F contains a magnetic domain wall, [24][25][26][27][28][29][30] the junction consisting of multilayers of Fs, [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] or spin active interface at the S/F interface . [47][48][49][50][51][52][53][54] The penetration length of STC with spin…”